Flow through pipet

ABSTRACT

The present invention is directed to a flow through pipet for sample measurement. The pipet of the invention has a body defining an interior space for receiving a fluid. The drain line is provided to drain fluid above a drain line inlet, thereby establishing a repeatable upper fluid level in the body. A dispense valve on the lower end of the body selectively permit dispensing of the fluid from the body. A restriction member may be located in the interior space of the body for defining a passageway. The drain line inlet may communicate with the passageway to establish a smaller surface area for an upper surface of the fluid, thereby minimizing a variance in the fluid level. A vent line vents gas from the measuring chamber during filling of a fluid. The pipet of the invention is particularly suitable for use in an automated system due to the top fill feature, which eliminates the need for cycling back and forth between a fill vessel and a dispense vessel. Additionally, the invention is suitable for use in an automated system utilizing a multi-pipet assembly, wherein multiple pipets may be filled simultaneously or in any manner desired.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to a pipet used to measure adiscrete amount of a fluid. More particularly, the invention relates toa flow through pipet, wherein a fluid is delivered to the pipet througha first end and a predetermined amount of fluid is dispensed through asecond end.

[0003] 2. Background

[0004] Pipets are used to extract, measure and transfer a pre-determinedvolume of a fluid. A typical pipet draws fluid by suction from a fluidsource and then dispenses the fluid volume into a receiving vessel.Pipets are typically used in laboratory and clinical environments. Atypical pipet includes a cylindrical vessel that is open at both endsand has a mark specifying a predefined volume and a means to applypressure and suction to one end of the vessel.

[0005] In use, one end of the pipet is immersed in a source of fluid andsuction is applied to the vessel at the other end. The operator adjuststhe level of fluid in the vessel to a specified mark. Next, the pipet ispositioned to access a receiving vessel and pressure or gravity forcesthe fluid out of the pipet into the receiving vessel. The pipet is thenwithdrawn from the receiving vessel and is relocated to prepare tointake the next volume of fluid from the same or another fluid source.

[0006] In addition to manual pipets, automated pipet systems have beendeveloped. An example automated pipet system may include a syringe, astepper motor, a three-way valve to select between intake and dispensefunctions, and equipment necessary to move the pipet vertically in andout of a fluid as well as equipment necessary to move the pipehorizontally from an intake location to a dispense location. Although ameans to apply pressure and suction has been automated and the movementof the pipet in the x and y directions has been automated, typically thesame basic design is used, wherein a cylindrical vessel is opened atboth ends. Examples of typical “glass straw” pipet vessels may be foundin U.S. Pat. Nos. 3,992,947, 4,476,095, 4,624,147, 5,090,255, 5,271,902,5,679,575, 5,820,824, and 6,253,628.

[0007] A drawback with typical manual pipets and with typical automatedpipets is that fluid is drawn into the pipet and dispensed from thepipet through the same orifice, which is usually located at the lowerend of the pipet. Filling and dispensing of fluid from the same orificein the pipet necessitates locating the pipet in a fluid source to fillthe pipet and then relocating the pipet at a dispensing location everytime it is desired to dispense a sample of fluid. Consequently,automated pipet systems require complex systems to relocate the pipetfrom the fluid source to the dispensing location.

[0008] A pipet is desirable that is capable of delivering a repeatablepredetermined volume of fluid, wherein the pipet fills from the top anddispenses from the bottom, i.e., a flow through pipet. It is furtherdesirable to provide a top fill pipet that does not trap air in themeasuring chamber. Such a pipet could be provided in an automatedpipetting system wherein the pipet would not have to be repositioned toa fill location after dispensing a fluid sample, thereby greatlysimplifying an automated pipetting system.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to a flow through pipet forfluid measurement. The pipet of the invention has a body defining aninterior space for receiving a fluid. The drain line is provided todrain fluid in the interior space above a drain line inlet, therebyestablishing a repeatable upper fluid level in the body. A dispensevalve on the lower end of the body selectively permits dispensing of thefluid from the body.

[0010] A restriction member may be located in the interior space of thebody for defining a passageway. The drain line inlet preferablycommunicates with the passageway. By locating the drain line inlet inthe restriction member passageway, a smaller surface area of an uppersurface of the fluid is exposed, thereby minimizing a variance in thefluid level. The drain line inlet establishes an upper end of ameasuring chamber and also establishes a lower end of an overflowchamber.

[0011] The flow through pipet may further include a vent line thatcommunicates the overflow chamber with the measuring chamber, whichallows trapped gas to escape from the measuring chamber during fillingof a fluid. A fill valve may be provided in the interior space, whereinthe fill valve defines an upper end of an overflow chamber and a lowerend of a fill chamber. The fill valve selectively permits fluid to passfrom the fill chamber to the overflow chamber.

[0012] A compressed gas line may be provided that is in communicationwith the overflow chamber for delivering compressed gas to the interiorspace. A junction for separating the body into an upper segment and alower segment is provided so that the body can be disassembled, therebypermitting the attachment of a lower segment of a desired volume to beaffixed to the upper segment.

[0013] In use, a fluid is delivered into a measuring chamber through anupper end of a pipet body to fill the measuring chamber with a fluid.Fluid in excess of a predetermined amount is drained out of the drainline. The draining of excess fluid establishes an upper fluid level inthe measuring chamber so that a predetermined volume of sample fluid maybe established in the measuring chamber. During delivery of the fluidinto the measuring chamber, gas may be vented from the measuring chambervia a separate pathway simultaneous to the filling of the measuringchamber with fluid.

[0014] Fluid may be delivered into the measuring chamber through anupper end of the body from an attached supply source, which may bedesirable in an automated process. Preferably, the filling anddelivering steps are achieved without moving the body in an X or Ydirection. Compressed gas may be delivered into the body above thesample chamber to force the fluid out of the body or the fluid may bedelivered by gravity feed.

[0015] A better understanding of the present invention, its severalaspects, and its advantages will become apparent to those skilled in theart from the following detailed description, taken in conjunction withthe attached drawings, wherein there is shown and described thepreferred embodiment of the invention, simply by way of illustration ofthe best mode contemplated for carrying out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Referring now to the drawings wherein like elements retain thesame numerical designation in the several figures.

[0017]FIG. 1 is a schematic view of a pipet of the invention for sampleor reagent measuring;

[0018]FIG. 2 is a schematic view of a pipet of the invention having aremote fluid supply, a pump, and a recirculation line for recirculatingexcess fluid;

[0019]FIG. 3 is a schematic view of a pipet of the invention having acontinuous supply source;

[0020]FIG. 4 is a schematic view of a pipet of the invention suitablefor use with small volumes of fluid;

[0021]FIG. 5 is a schematic view of another embodiment of a pipet of theinvention suitable for use with small volumes of fluid.

[0022]FIG. 6 is a schematic view of the pipet of the inventionincorporated into a multi-pipet assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] Before explaining the present invention in detail, it isimportant to understand that the invention is not limited in itsapplication to the details of the embodiments and steps describedherein. The invention is capable of other embodiments and of beingpracticed or carried out in a variety of ways. It is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and not of limitation.

[0024] Referring now to FIGS. 1-6 shown are embodiments of a flowthrough pipet designated generally 10. Pipet 10 has a body 12. Body 12has an upper end 14, a lower end 16 and defines an interior space 18.Supplied fluid is delivered to interior space 18 through or proximate toupper end 14.

[0025] In one embodiment, shown in FIG. 2, a fill line 20 is providedthat communicates a remote fluid supply source 22 to interior space 18.Remote fluid supply source 22 may be a supply pump reservoir or otherfluid supply source. Fill line 20 preferably communicates with interiorspace 18 proximate upper end 14 of body 12. A fill line valve 24 ispreferably provided to control fluid flow from the fluid supply source22.

[0026] In another embodiment, shown in FIG. 3, the upper end 14 of body12 communicates with a continuous supply source 26. Examples of acontinuous supply source 26 include a process pipe, tank or othersource. As shown in FIG. 3, a measured volume of fluid may be collectedfrom process pipe 28. Still referring to FIG. 3, an isolation valve 30is preferably provided to selectively allow supplied fluid into interiorspace 18 from the continuous supply source 26.

[0027] Referring back to FIGS. 1-3, a restriction member 32 may beprovided in interior space 18 of body 12. Restriction member 32 has alower surface 34, which may be conically shaped. Restriction member 32additionally has an upper surface 36 which is preferably conical toassist in directing fluid toward a reduced area passageway 38. Reducedarea passageway 38 is defined by inner walls 40 located between uppersurface 36 and lower surface 34.

[0028] Still referring to FIGS. 1-3, drain line 42 has a inlet 44 thatcommunicates with passageway 38 in interior space 18. When a restrictionmember 32 is used, drain line 42 preferably communicates with passageway38. Placing inlet 44 in passageway 38 is advantageous because passageway38 has a reduced diameter as compared to a diameter of body 12. Thereduced diameter passageway 38 results in a reduced diameter of an uppersurface of the fluid, thereby yielding a greater accuracy with respectto the fluid volume. A drain line valve 46 is provided to selectivelyopen or close drain line 42.

[0029]FIGS. 4 and 5 disclose pipets suitable for use with small volumesof fluid. Additionally, the pipets of FIGS. 4 and 5 could be used withany volume of fluid when less precision is required. The pipets of FIGS.4 and 5 have no restriction members therein. Therefore, inlet 44 ofdrain line 42 communicates with interior space 18.

[0030] Inlet 44 defines an upper end of a measuring chamber 54 ininterior space 18. Additionally, inlet 44 defines a lower end of anoverflow chamber 56 in the interior space 18 (FIGS. 1-3). In allembodiments, drain line 42 defines a repeatable upper fluid level of theinterior space 18 of pipet 10.

[0031] In one embodiment, shown in FIG. 2, drain line 42 communicateswith a pump 48, which is used to draw excess fluid from interior space18. The excess fluid may then be pumped through recirculation line 49back to remote fluid supply source 22 or discarded as desired. Stillreferring to FIG. 2, if a drain line pump 48 is used to suck excessfluid from the interior space 18, then it is desirable to provide apressure equalization line 50 with a pressure equalization valve 52 toallow gas to enter interior space 18 when drain line pump 48 isactivated.

[0032] Referring now to FIGS. 1 and 3-5, a fill valve 58 is located inbody 12 to isolate a fluid supply from a measured fluid that is locatedin measuring chamber 54. Fill valve 58 defines an upper end of overflowchamber 56 and defines a lower end of fill chamber 60 (FIGS. 1 and 3-5).Fill valve 58 selectively permits fluid to pass from fill chamber 60 tooverflow chamber 56.

[0033] Referring now to FIGS. 1, 2 and 4, a vent line 62 is providedthat communicates the overflow chamber 56 with measuring chamber 54. Asshown in FIGS. 1, 2 and 4, vent line 62 is located in the interior space18 of body 12. It is desirable to provide a weather cap 64 (FIGS. 1, 2and 4) on an upper end of vent line 62 so that when fluids are deliveredto interior space 18, fluids are prevented from entering an upper end ofthe vent line 62.

[0034] In other embodiments, as shown in FIGS. 3 and 5, vent line 62communicates with an exterior of body 12. In embodiments having anexterior vent line 62, it may be desirable to provide a vent valve 66(FIGS. 3 and 5).

[0035] A compressed gas line 68 may be provided for communicating acompressed gas source with interior space 18 (FIGS. 1-6). A compressedgas valve 70 may be provided to control access of compressed gas to thebody 12. Compressed gas may be useful in forcing fluids out of lower endof 16 the pipet 10. However, compressed gas may be substituted by theuse of gravity to dispense fluids from the body 12 with the pipet 10 ofthe invention.

[0036] A dispense valve 72 is provided on lower end 16 of body 12.Dispense valve 72 allows for selective dispensing of a fluid frommeasuring chamber 54. Dispense valve 72 may be any type of suitablevalve known in the art. However, in a preferred embodiment, dispensevalve 72 is pressure actuated. Additionally, dispense valve 72 may bemanually actuated, electronically actuated, or actuated by other means.

[0037] A junction 74 may be provided so that body 12 is separatable intoan upper segment 76 and a lower segment 78. Upper segment 76 and lowersegment 78 may be connected at junction 74 by threads, cooperatingdetents and protrusions, clips or other means.

[0038]FIG. 6 shows a multi-pipet assembly 80 having a fill line 20 thathas multiple branches that communicate a remote fluid supply source 22to interior space 18 a and 18 b of bodies 12 a and 12 b, respectively.Although only two pipet bodies, 12 a and 12 b, are shown for purposes ofexample, it should be noted that any number of pipet bodies 12 a, 12 b,12 c . . . may be incorporated into the multi-pipet assembly 80 of theinvention. It should also be noted that like elements of multi-pipetassembly 80 to elements of embodiments shown in FIGS. 1-5 have retainedthe same numerical designation in FIG. 6, with the exception that “a” or“b” has been appended to some of the numbers to designate to which ofthe pipet bodies 12 a, b that the numeral designations refer. Forexample, in a manner similar to that of the embodiment of FIG. 2, drainline pump 48 draws excess fluid from interior space 18 a and 18 bthrough drain line branches 42 a and 42 b. The excess fluid may then bedirected through recirculation line 49 back to remote fluid supplysource 22 or discarded as desired. A single pressure equalization line50 and compressed gas line 68 may be provided, which are capable ofacting upon interior spaces 18 a, 18 b, etc., since interior spaces 18a, 18 b, etc. communicate with one another via passageway 82.Alternatively, pressure equalization line 50 and compressed gas line 68may provide individual branches for communicating with each of interiorspaces 18 a, 18 b, etc.

[0039] In use, a fluid is delivered into measuring chamber 54 through anupper end 14 of body 12. Fluid in excess of a desired amount drains outof drain line 42. By draining fluid out of drain line 42, an upper fluidlevel is established in interior space 18. The upper fluid level definesa predetermined volume of fluid in measuring chamber 54. Thepredetermined volume of fluid may then be dispensed out of lower end 16of body 12 through dispense valve 72. The dispense valve 72 may beelectronically actuated, manually actuated or actuated by other methods.

[0040] In one embodiment, e.g., as shown in FIGS. 1-3 and 6, the surfacearea of the fluid may be restricted or reduced in size as compared tothe dimensions of the interior space 18 by providing a restrictionmember 32. For example, the drain line 42 may be located to communicatewith an inner wall 40 of a restriction member 32, thereby establishingan upper fluid level having a reduced or restricted service area.Minimizing the surface area of the fluid surface minimizes measurementerror of the pipet.

[0041] To prevent gas from being trapped in the measuring chamber 54, avent line 62 (FIGS. 1-6) may be provided. By separating the vent line 62from the passageway 38 (FIGS. 1-3 and 6), gas may simultaneously escapefrom measuring chamber 54 while measuring chamber 54 is being filledwith the fluid.

[0042] The delivery of fluid into interior space 18 may be accomplishedvia a fill line 20 (FIGS. 2 and 6), which delivers fluid to an areaproximate upper end 14 of the body 12. Additionally, fluid may bedelivered directly into upper end 14 of body 12 via manual delivery ordelivery from a remote fluid supply source 22 (FIGS. 2 and 6) or acontinuous supply source 26 (FIG. 3).

[0043] Referring back to FIGS. 2 and 6, it may be desirable to provide apump 48 for sucking excess fluid from the interior space 18. To minimizewaste of the fluid, a recirculation line 49 may be provided to routeexcess fluid back to a remote fluid supply source 22 where the fluid canbe reintroduced into the interior space 18 via fill line 20.

[0044] Dispensing the predetermined volume of fluid may be achieved bygravity feed or, alternatively, by delivering compressed gas into theinterior space 18 to force the fluid out of lower end 16 of body 12. Todeliver compressed gas to interior space 18, compressed gas valve 70 isopened and gas is delivered through line 68 into interior space 18 at alocation above the drain line 42.

[0045] Referring now to FIGS. 4 and 5, for dispensing very small amountsof a predetermined volume of fluid, it may be unnecessary to provide arestriction member 32, as shown in FIGS. 1-3, in the interior space 18of the body 12. However, it may still be desirable to provide astructure for venting gas from measuring chamber 54 when fluid isdelivered to the measuring chamber 54. In particular, for a very smalldiameter of body 12, incoming fluid may not readily permit trapped gasto escape. Therefore, in one embodiment, vent line 62 may be providedwithin interior space 18, where the vent line 62 has a lower opening ata location below the inlet 44 of drain line 42 and has an upper openingat a location above the inlet 44 of drain line 42. Weather cap 64 ispreferably provided above the vent line 62 of FIG. 4 to prevent fluidfrom entering the upper opening of vent line 62. In another embodiment,as shown in FIG. 5, the vent line 62 may be provided externally to thebody 12. A vent valve 66 may be provided on vent line 62.

[0046] Referring back to FIG. 3, delivery from a continuous supplysource 26 may be desirable to provide a sampling device for a processstream. In this embodiment, isolation valve 30 is selectively opened toadmit fluid from process pipe 28. The fluid then fills the fill chamber60. Fill valve 58 may then be opened to allow the fluid to pass from thefill chamber 60 through overflow chamber 56, through passageway 38 andinto measuring chamber 54. As the fluid fills measuring chamber 54,displaced gas is vented out through vent line 62. In this embodiment,the vented gas is vented to an exterior of body 12 through vent line 62.Once the fluid level in the measuring chamber 54 rises to the inlet 44of level of the drain line 42, any excess fluid is drained out ofinterior space 18, e.g., any fluid rising into overflow chamber 56 willbe drained out of interior space 18, thereby establishing a maximumvolume of fluid in the measuring chamber 54.

[0047] If it is desired to use a pipet 10 having a fill valve 58, adrain valve 46 on a drain line 42, a gas valve 70 on a compressed gasline 68 and a dispense valve, then a prescribed sequence of opening andclosing various valves 58, 46, 70 and 72 is desirable for operating thepipet. Below is an example sequence of valve operation. The valveoperation may be varied without adversely effecting the accuracy andprecision of the inventive pipet.

[0048] Description of Steps:

[0049] 0. Start with valves 46, 58, 70 and 72 closed.

[0050] 1. Fluid is delivered through the fill valve 58. The fluid flowsthrough the passageway 38 through the restriction member 32 and into themeasuring chamber 54.

[0051] 2. The drain valve 46 is opened and excess liquid drained out ofthe manifold.

[0052] 3. The fill valve 58 is closed.

[0053] 4. Gas valve 70 is opened briefly to ensure that excess liquiddrains through the drain valve 46 and into drain line 42.

[0054] 5. The drain valve 46 is closed.

[0055] 6. The compressed gas valve 70 is opened. The increased pressureinside interior space 18 activates a pressure actuated dispense valve 72to allow the measured liquid within measuring chamber 54 to exit via theopen dispense valve 72.

[0056] 7. The compressed gas valve 70 is closed.

[0057] 8. The drain valve 46 is opened to relieve pressure.

[0058] 9. Step 5 is repeated

[0059] 10. Step 6 is repeated

[0060] 11. Step 7 is repeated

[0061] 12. Step 8 is repeated

[0062] 13. Step 9 is repeated

[0063] Alternatively, step 9 could comprise “close drain valve 46” andsteps 10-13 could be eliminated. Steps 10-13 are cautionary to ensurethat all measured liquid has been discharged.

[0064] Steps for one method of operation are presented in the belowTable. Dispense Step Fill Valve 58 Drain Valve 46 Gas Valve 70 Valve 720 Close Close Close Close 1 Open Close Close Close 2 Open Open CloseClose 3 Close Open Close Close 4 Close Open Pulse Close 5 Close CloseClose Close 6 Close Close Open Open 7 Close Close Close Close 8 CloseOpen Close Close 9 Close Close Close Close 10 Close Close Open Open 11Close Close Close Close 12 Close Open Close Close 13 Close Close CloseClose

[0065] As described above, a novel pipet is taught for automatically andinexpensively extracting an aliquot of liquid from one source, measuringa predetermined volume of the liquid and transferring the volume ofliquid to a different vessel. Benefits of the novel pipet includesimplicity and therefore low expense to manufacture, ease of automation,minimization of the volume of liquid that must be used to rinse theapparatus, elimination of a need to reposition the pipet after liquidhas been introduced into the pipet, elimination of expensive syringepumps that are used in typical automated pipetting systems, eliminationof the use of suction to fill the pipet with liquid, and use of gravityand overflow rather than a syringe pump to measure volume.

[0066] While the invention has been described with a certain degree ofparticularity, it is understood that the invention is not limited to theembodiment(s) set for herein for purposes of exemplification, but is tobe limited only by the scope of the attached claim or claims, includingthe full range of equivalency to which each element thereof is entitled.

What is claimed is:
 1. A flow through pipet for fluid measurementcomprising: a body defining an interior space for receiving a fluid; adrain line having an inlet, said drain line communicating said interiorspace with an exterior of said body; a dispense valve on a lower end ofsaid body for selectively emptying fluid from said body; wherein saiddrain line is for draining fluid above said inlet, thereby establishinga repeatable upper fluid level in said body.
 2. The flow through pipetaccording to claim 1 further comprising: a restriction member located insaid interior space of said body, said restriction member defining apassageway; and wherein said inlet of said drain line communicates withsaid passageway.
 3. The flow through pipet according to claim 2 furthercomprising: a measuring chamber in said interior space defined at anupper end by said drain line inlet; a vent line that communicates saidmeasuring chamber with a location above said drain line inlet forallowing gas to escape from said measuring chamber during filling ofsaid measuring chamber with fluid.
 4. The flow through pipet accordingto claim 1 further comprising: a measuring chamber in said interiorspace defined at an upper end by said drain line inlet; a vent line thatcommunicates said measuring chamber with a location above said drainline inlet for allowing gas to escape from said measuring chamber duringfilling of said measuring chamber with fluid.
 5. The flow through pipetaccording to claim 1 further comprising: a fill valve in said interiorspace, said fill valve defining an upper end of an overflow chamber,said fill valve for selectively permitting fluid to pass into saidoverflow chamber.
 6. The flow through pipet according to claim 1 furthercomprising: a compressed gas line in communication with said interiorspace at a location above said drain line inlet for communicating acompressed gas source with said interior space.
 7. The flow throughpipet according to claim 1 further comprising: a junction for separatingsaid body into an upper segment and a lower segment for permitting alower segment of a selected volume to be affixed to said upper segment.8. The flow through pipet according to claim 1 further comprising: apump for drawing excess fluid out of said drain line.
 9. The flowthrough pipet according to claim 1 wherein said upper end of said bodyreceives sample fluid from a continuous supply source.
 10. The flowthrough pipet according to claim 1 further comprising: a fill line fordelivering fluid to said interior space.
 11. The flow through pipetaccording to claim 1 wherein: said body is one of a plurality of bodiesforming a multi-pipet assembly.
 12. The flow through pipet according toclaim 11 wherein: said interior space within each of said plurality ofbodies communicate with one another via a passageway.
 13. The flowthrough pipet according to claim 11 further comprising: a fill line incommunication with said interior space of each of said plurality ofbodies.
 14. A pipet for fluid measurement comprising: a body having anupper end, a lower end and defining an interior space; a restrictionmember located in said body, said restriction member having a lowersurface, an upper surface, and having inner walls between said uppersurface and said lower surface, said inner walls defining a passageway;a drain line having an inlet, said drain line communicating saidpassageway with an exterior of said body; said inlet defining an upperend of a measuring section of said interior space and defining a lowerend of an overflow section in said interior space; a dispense valve onsaid lower end of said body for selectively emptying fluid from saidmeasuring section of said body; wherein said drain line is for drainingfluid above said inlet, thereby establishing a repeatable upper maximumfluid level in said measuring section.
 15. The flow through pipetaccording to claim 14 further comprising a vent line for venting trappedgas from said measuring section to a location above said drain lineinlet.
 16. The flow through pipet according to claim 14 wherein: saidbody is one of a plurality of bodies forming a multi-pipet assembly. 17.A method of pipetting fluids comprising the steps of: delivering a fluidinto a measuring chamber through an upper end of a body; filling saidmeasuring chamber with said fluid; draining said fluid out of a drainline to establish an upper fluid level in said measuring chamber therebydefining a predetermined volume of fluid in said measuring chamber; anddelivering said predetermined volume of fluid out of a lower end of saidbody.
 18. The method according to claim 17 further comprising the stepof: restricting a surface area of said upper fluid level for minimizingmeasurement error of said predetermined volume of fluid.
 19. The methodaccording to claim 17 further comprising the step of: venting gas fromsaid measuring chamber via a separate pathway simultaneously to saidstep of filling said measuring chamber with said fluid.
 20. The methodaccording to claim 17 wherein: said step of delivering fluid into ameasuring chamber through an upper end of a body comprises deliveringfluid from an attached supply source.
 21. The method according to claim20 wherein: said filling and delivering steps are achieved withoutmoving said body in a horizontal direction.
 22. The method according toclaim 17 wherein said step of delivering fluid further comprises:delivering fluid into measuring chambers of multiple bodies comprising amulti-pipet assembly.
 23. The method according to claim 17 wherein: saidstep of delivering said predetermined volume of fluid comprises applyingcompressed gas above said measuring chamber to force said sample fluidout of said body.
 24. The method according to claim 17 wherein: saidstep of delivering said predetermined volume of fluid comprises allowinggravity to dispense said fluid out of said body.
 25. The methodaccording to claim 17 further comprising a step of: recirculating fluiddrained from said drain line through a recirculation line and into saidupper end of said body.